The present invention relates to material removing tools in general, and more particularly to improvements in rotary tools wherein the cutting elements are relatively thin blades which are installed in discrete holders and are subjected to pronounced wear so that they must be inspected, mounted in different positions or replaced at frequent intervals. For example, the tool of the present invention can be used to produce shavings or chips of accurately determined thickness from pieces of wood or the like preparatory to use of shavings in the manufacture of composition panels or the like.
It is known to produce shavings of wood by means of a tool wherein a rotary main body portion supports several discrete holders for thin plate- or sheet-like blades whose cutting edges extend beyond the peripheral surface of the tool so as to remove shavings of predetermined thickness while the tool rotates and is being fed against the piece of wood or vice versa. As a rule, the holders are urged against the body portion of the tool by spring-biased wedges which are mounted in such a way that, when the tool rotates, centrifugal force urges the wedges against the adjacent holders to thus assist the action of one or more springs. The holders cannot move radially of the tool, i.e., they cannot shift the cutting edges of the blades toward or away from the axis about which the main body portion of the tool rotates.
The operating cost of machines which utilize the just described tools depends to large extent on the cost of blades and on the length of intervals which are required to replace a used blade with a fresh blade or to change the orientation of a blade having several cutting edges. The cost of blades is reduced by using polygonal pieces of flat sheet steel stock having one or more cutting edges. The length of intervals which are required for exchange or reorientation of blades can be reduced by using holders which can be rapidly inserted into or removed from the body portion of the tool. A further important factor which determines the cost of operation is the manner of and the time required for adjustment of blades with or relative to their holders so as to insure that the cutting edges will remove shavings or chips of desired thickness.
German Pat. Utility Model No. 1,952,986 discloses a rotary material removing tool wherein flat plate-like blades are inserted into U-shaped holders. The two legs of each U-shaped holder are biased against the respective major surfaces of a blade therebetween by screws whose heads bear against the outer side of one leg and whose shanks mate with internal threads of the other leg. Each package consisting of a U-shaped holder, a blade between the legs of the holder, and one or more screws is insertable into and removable from a discrete recess in the main body portion of the tool and is held therein by a spring-biased wedge. A drawback of such tools is that the replacement of a blade takes up a substantial amount of time. Thus, it is necessary to retract the wedge, to thereupon remove the package from its recess, to loosen the screws so as to permit removal of a worn blade, to insert a fresh blade, to tighten the screws, to reinsert the package into the recess, and to release the wedge in order to properly position the package so that the cutting edge of the blade can remove shavings of desired thickness.
German Pat. Utility Model No. 7,211,370 discloses a modified rotary tool wherein each U-shaped holder for a flat blade consists of two separable sections which abut against each other in the region where the two legs of the U meet. The blade is accessible upon detachment of that section which is adjacent to a retractible spring-biased wedge, and the sections have complementary male and female portions which hold the detachable sections against movement radially of the rotary tool. The just described construction simplifies, to a certain extent, the replacement of blades because it is not necessary to remove the entire holder from the rotary body portion. Nevertheless, the replacement of a blade still takes up an excessive amount of time, especially in view of the fact that the useful life of a blade, or of a cutting edge, is extremely short so that the replacement or reorientation of blades must take place at frequent intervals. Moreover, the adjustment of holders and/or blades in the aforedescribed conventional tools is complex and time-consuming.
German Pat. Utility Model No. 7,214,461 discloses a further rotary tool which employs apertured blades. The blades are insertable between the legs of U-shaped holders, together with strip-shaped retaining members which are formed with projections extending into the apertures of adjoining blades. The position of each retaining member with respect to the corresponding holder can be adjusted by an eccentric to thereby select the distance between the cutting edge of the blade and the axis of rotation of the tool. The just described construction simplifies the adjustment of blades but the replacement of a blade still takes up an inordinately large amount of time because each holder must be removed from the main body portion in its entirety, the screws which hold the retaining member between the legs of the removed holder must be detached, the retaining member must be withdrawn together with a spent blade, a fresh blade attached to the retaining member, the retaining member reinserted into the holder, the screws reattached to the holder, and the holder reinserted into the main body portion. Furthermore, it is necessary to insert each holder into one and the same recess because the manufacturing tolerances are such that the insertion of a holder into a different recess would invariably necessitate an adjustment of the respective retaining member with attendant losses in time. Therefore, such tools are normally furnished with two holders for each recess in the main body portion so that one holder is ready for insertion when the other holder is removed. This reduces the length of intervals of stoppage but contributes significantly to the initial cost of the tool. Moreover, each holder and each recess must be numbered to insure that the operator can rapidly locate that recess which is to receive a particular holder.